MEMS device positioning apparatus, test system, and test method

ABSTRACT

A positioning apparatus includes a support structure, a positioning structure, and a fixture for retaining MEMS devices. A shaft spans between the support structure and the positioning structure, and is configured to rotate about a first axis relative to the support structure in order to rotate the positioning structure and the fixture about the first axis. The positioning structure includes a pair of beams spaced apart by a third beam. Another shaft spans between the pair of beams and is configured to rotate about a second axis relative to the positioning structure in order to rotate the fixture about the second axis. Methodology entails installing the positioning apparatus into a chamber, orienting the fixture into various positions, and obtaining output signals from the MEMS devices to determine functionality of the MEMS devices.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to microelectromechanicalsystems (MEMS) devices. More specifically, the present invention relatesto a positioning apparatus, test system, and methodology for costeffectively testing a MEMS device in a plurality of positions.

BACKGROUND OF THE INVENTION

Microelectromechanical systems (MEMS) devices are used in a wide varietyof products such as automobile airbag systems, control applications inautomobiles, navigation, display systems, inkjet cartridges, and soforth. MEMS devices include, for example, pressure sensors,accelerometers, gyroscopes, microphones, digital mirror displays, microfluidic devices, and so forth. Continuous progress is being made in MEMSdevice technology and fabrication efficiency. Indeed, productivity gainsfrom advances in MEMS device technology and fabrication efficiencyunderlie the modern economy, making it possible to implement variousMEMS devices in a wide variety of products.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be derived byreferring to the detailed description and claims when considered inconnection with the Figures, wherein like reference numbers refer tosimilar items throughout the Figures, the Figures are not necessarilydrawn to scale, and:

FIG. 1 shows a block diagram of a test system in accordance with anembodiment;

FIG. 2 shows a perspective view of an exemplary test system;

FIG. 3 shows a side view of the test system;

FIG. 4 shows a front view of a portion of the test system;

FIG. 5 shows a side view of a positioning apparatus of the test system;

FIG. 6 shows a simplified side view of a portion of a rotational drivesystem implemented within the test system;

FIG. 7 shows a simplified side view of another portion of the rotationaldrive system implemented within the test system;

FIG. 8 shows a cut away partial top view of a positioning structure ofthe test system;

FIG. 9 shows a simplified partial front view exemplifying thepositioning apparatus of the test system placed in a first position;

FIG. 10 shows a simplified partial front view exemplifying thepositioning apparatus of the test system placed in a second position;

FIG. 11 shows a simplified partial side view exemplifying thepositioning apparatus of the test system placed in a third position; and

FIG. 12 shows a flowchart of a temperature test process performed usingthe test system in accordance with another embodiment.

DETAILED DESCRIPTION

MEMS devices typically undergo comprehensive calibration and testingfollowing fabrication. The degree of MEMS device testing depends uponthe functionality of the MEMS device. However, an inherent temperaturesensitivity of MEMS devices typically requires temperature testing toverify accuracy of the MEMS devices over a range of operationaltemperatures. Therefore, temperature testing with cold, ambient, and hotconditions is typically performed. Such a temperature test for MEMSdevices is generally referred to as a tri-temperature (or simplytri-temp) thermal conditioning. Tri-temp thermal conditioningcharacterizes or tests the functionality of MEMS devices over a range oftemperatures, for example, between −55° C. and +180° C. Tri-temp thermalconditioning can be used to determine resilience to temperaturevariation on the mechanical and electrical performance of the MEMSdevices in order to ensure the accuracy and safety of the MEMS devices.

Unfortunately, the cost of MEMS device testing consumes an inordinateshare of productions costs. Indeed, some estimates place the cost ofMEMS device testing from between twenty to thirty percent based upon thedevice and its intended application. However, increasing productionvolumes and requirements for lower test costs continuously drives MEMSmanufacturers to seek more efficient testing methods.

Embodiments entail a positioning apparatus, test system, and methodologyfor testing MEMS devices. In particular, embodiments enable MEMS devicesto be tested in various positions and over a range of temperatures. Thetest system includes multiple axis control that minimizes operatorinvolvement in a test process such as during thermal conditioning and/orcalibration, while achieving improvements in position accuracy, MEMSdevice throughput, and reduced test time. Accordingly, MEMS devices canbe trimmed and qualification readouts can be performed at significantcost savings.

FIG. 1 shows a block diagram of a test system 20 in accordance with anembodiment. Test system 20 may be utilized to perform tri-temp thermalconditioning on one or more MEMS devices 22. MEMS devices 22 may beaccelerometers, gyroscopes, magnetometers, or any of a variety of MEMSdevices.

Test system 20 generally includes a chamber, referred to herein as athermal chamber 24, a positioning apparatus 26, a control unit 28, and atest unit 30. Thermal chamber 24 is configured to hold a portion ofpositioning apparatus 26 within its interior space 32. Thermal chamber24 includes one or more thermal elements 34 which may be controlled by atemperature control circuit 36 for cooling and/or heating interior space32. Temperature control circuit 36 and thermal elements 34 may beadapted to provide a range of temperatures between, for example, −55° C.and +180° C. Thermal chamber 24 may further include a fan 38 which maybe controlled by a fan control circuit 40 for circulating air withininterior space 32. Thermal chamber 24 can be used to providetri-temperature thermal conditioning and/or any other low-g applicationtemperature testing.

In an embodiment, a portion of positioning apparatus 26 is configured tobe installed into interior space 32 of thermal chamber 24. Inparticular, positioning apparatus 26 includes a positioning structure 42and a fixture 44 which can be installed within thermal chamber 24.Positioning structure 42 is adapted to place fixture 44 in variouspositions. A position sensor 46 may be attached to fixture 44 to provideposition measurement of fixture 44. Position sensor 46 may be anabsolute position sensor or a relative one (displacement sensor).Position sensor 46 may provide output signals 48, 50 pertaining to theposition of fixture 44 relative to two axes within a three-dimensionalcoordinate system. Of course, position sensor 46 may additionallyprovide output signals relative to all three axes within athree-dimensional coordinate system.

Fixture 44, sometimes referred to as a load board or carrier, is adaptedto hold a plurality of MEMS devices 22 in a fixed and known position.Fixture 44 may be suitably wired to output pins (not shown) of MEMSdevices 22 so as to route device output signals 52 from MEMS devices 22.In some embodiments, fixture 44 can retain a plurality of MEMS devices22 for concurrent testing. Accordingly, testing may produce distinctoutput signals 52 for each MEMS device 22 under test. These distinctoutput signals 52 are represented by the terms O₁, O₂, O₃ to O_(N),where “O” represents “output” and “N” represents the total number ofMEMS devices 22 being tested.

Positioning system 26 further includes a rotational drive system 54located external to thermal chamber 24. In accordance with anembodiment, rotational drive system 54 is configured to enable rotationof positioning structure 42 along with fixture 44 about an axis 56,labeled “X-AXIS” in FIG. 1. Rotational drive system 54 is additionallyconfigured to enable rotation of fixture 44 about another axis 58,labeled “Y-AXIS” in FIG. 1. For exemplary purposes, rotational drivesystem 54 is illustrated herein as including a motor 60 for enablingrotation of positioning structure 42 about X-axis 56, and as including amotor 62 for enabling rotation of fixture 44 about Y-axis 58. Motors 60and 62 may be embodied in a dual axis motor 64. Alternatively, motors 60and 62 may be embodied as two distinct single axis motors. Motors 60 and62 enable rotation of positioning structure 42 and fixture 44 viaelectric power. Accordingly, an electrical plug 63 is provided in FIG. 1to represent the provision of electricity to electrically power motors60 and 62.

Control unit 28 is adapted to control the operation of temperaturecontrol circuit 36, fan control circuit 40, and rotational drive system54. Control unit 28 may be a conventional computing system including aprocessor, monitor, keyboard, mouse, as known to those skilled in theart. An operator using control unit 28 and executing program code atcontrol unit 28 may send control signals to temperature control circuit36, fan control circuit 40, and rotational drive system 54. Thesecontrol signals may include for example, a fan on/off signal 65 (labeledFAN), a temperature setting signal 66 (labeled TEMP), an X-axis controlsignal 68 (labeled CS_(X)), and a Y-axis control signal 70 (labeledCS_(Y)).

In general, fan on/off signal 65 signals fan control circuit 40 toenergize or de-energize fan 38. Temperature setting signal 66 signalstemperature control circuit 36 to heat or cool interior space 32 ofthermal chamber 24 to a particular temperature setting. The temperatureof interior space 32 may be monitored via a temperature sensor locatedwithin interior space 32 that communicates a temperature signal 72 totemperature control circuit 36 and/or to control unit 28. X-axis controlsignal 68 signals motor 60 to rotate positioning structure 42, as wellas fixture 44, to a predetermined position. Similarly, Y-axis controlsignal 70 signals motor 62 to rotate fixture 44 to a predeterminedposition. Exemplary positions in accordance with particular testmethodology will be discussed in connection with FIGS. 9-11.

Test unit 30 is adapted to receive device output signals 52, O₁, O₂, O₃,. . . O₄, from MEMS devices 22 during testing. Test unit 30 may beanother conventional computing system including a processor, monitor,keyboard, mouse, and the like. Alternatively, test unit may be a specialpurpose computing unit. And in still other embodiments, test unit 30 andcontrol unit 28 may be combined in a single computing system.

In general, test unit 30 determines the functionality of MEMS devices 22in response to the received device output signals 52, as will bediscussed in accordance with test methodology set forth in FIG. 12. Thesignal lines for device output signals 52 at MEMS devices 22 arediscontinuous with the signal lines for device output signals 52 at testunit 30 for simplicity of illustration. Those skilled in the art willreadily recognize that physical wiring may be implemented to providedevice output signals 52 from MEMS devices 22 to test unit 30.Alternatively, device output signals 52 from MEMS devices 22 may beprovided to test unit 30 via wireless communications.

Referring to FIGS. 2-3 in connection with FIG. 1, FIG. 2 shows aperspective view of a test system 20 in an exemplary configuration, andFIG. 3 shows a side view of test system 20. Thermal chamber 24 mayreside on a housing 74 in which some or all of the various componentsexternal to thermal chamber 24 may be located. For example, control unit28, test unit 30, temperature control circuit 36, and/or fan controlcircuit 40 may be housed in housing 74. Test system 20 may furtherinclude a tray 76 upon which slide rails 78 are formed. Slide rails 78may be used to facilitate the movement of positioning apparatus 26 intoand out of interior space 32 of thermal chamber 24.

At least a portion of positioning apparatus 26 is configured to beplaced in interior space 32 of thermal chamber 24. For example,positioning structure 42 and fixture 44 are shown in interior space 32,as represented in dashed line form in FIG. 3. However, positioningapparatus 26 additionally comprises a support structure 80, and supportstructure 80 includes among other features a face section 82 having acompliant seal 84. Accordingly, when face section 82 is attached tothermal chamber 24, it forms a sealable door of chamber 24 withpositioning apparatus 26 and fixture 44 located within thermal chamber24. Additionally, dual axis motor 64 may be mounted on face section 82exterior to chamber 24. A gearbox 86 may house a gear mechanism(discussed below) for enabling rotation of positioning structure 26 aswill be discussed in significantly greater detail below.

FIG. 4 shows a front view of a portion of the test system 20. Inparticular, FIG. 4 shows a front view of face section 82 of positioningapparatus 26 attached to thermal chamber 24. Positioning apparatus 26includes receivers 88 that seat in slide rails 78 in order to readilyslide positioning apparatus 26 into place with thermal chamber 24. Afeedthrough port 90 is located in a center region of gearbox 86.Feedthrough port 90 enables the passage of a flexible shaft (discussedbelow), wiring, and the like into interior space 32 of thermal chamber24. Feedthrough port 90 includes any suitable sealing structure (notshown) that largely prevents ingress or egress of air from interiorspace of thermal chamber 24. Feedthrough port 90 is represented by wide,downwardly and rightwardly directed hatching to distinguish it from thesurrounding structures.

FIG. 5 shows a side view of positioning apparatus 26 of test system 20.Positioning apparatus 26 includes support structure 80, positioningstructure 42, and a shaft 92 spanning between and interconnected witheach of support structure 80 and positioning structure 42. In anembodiment, shaft 92 is configured to rotate about a first axis relativeto support structure 80. By way of example, shaft 92 is configured torotate about X-axis 56 in order to rotate positioning structure 42 andfixture 44 about X-axis 56.

Positioning structure 42 includes supporting members in the form offirst and second beams 94, 96 spaced apart from one another, and anotherbeam 98 spanning between and interconnected with each of beams 94, 96.Another shaft 100 is spaced between and interconnects with each of firstand second beams 94, 96. In an embodiment, each of beams 94, 96 has afirst end 102 and a second end 104. Beam 98 is interconnected with firstend 102 of each of beams 94, 96. Additionally, shaft 100 isinterconnected with beams 94, 96 at second end 102. Fixture 44 isretained on shaft 100 via, for example, mounting blocks 105. Thus,fixture 44 is fixed to, or immovable relative to, shaft 100. Shaft 100is configured to rotate about a second axis relative to positioningstructure 42, in which the second axis is orthogonal to the first axis.By way of example, shaft 100 is configured to rotate about Y-axis 58.Due to their fixed connection, when shaft 100 rotates about Y-axis 58,fixture 44 also rotates, or pivots, about Y-axis 58. Position sensor 46provides feedback of the actual position of fixture 44 relative toX-axis 56 and Y-axis 58 at a given instant.

In some embodiments, beams 94, 96, and 98 of positioning structure 42may be formed from a ceramic material such as alumina. Such a ceramicmaterial can provide temperature stability during tri-temp thermalconditioning since it does not flex or otherwise bend in response totemperature variations.

Now referring to FIG. 6 in connection with FIG. 5, FIG. 6 shows asimplified side view of a portion of a rotational drive system 54implemented within test system 20 (FIG. 1). In some embodiments,rotational drive system 54 includes motor 60 and a worm drive 106 thatcooperatively function to rotate, or pivot, positioning structure 42about a first axis, e.g., X-axis 56. Worm drive 106 includes a worm 108coupled with motor 60 and a worm gear 110 coupled with shaft 92. Wormdrive 106 is a gear arrangement in which worm 108 (in the form of ascrew) meshes with worm gear 110. Accordingly, worm 108 includes threads112 that mesh with teeth 114 of worm gear 110.

In operation, worm 108 is driven to rotate by motor 60. The relationshipof threads 112 with teeth 114 of worm gear 110 causes worm gear 110 torotate when worm 108 rotates. Since worm gear 110 is coupled to shaft92, shaft 92 rotates along with worm gear 110. Furthermore, since shaft92 is interconnected with positioning structure 42, positioningstructure 42 will also rotate, or pivot, to a desired position. In someembodiments, motor 60 may be a servomotor that includes a motor and arotary encoder combination that forms a servomechanism. The encoder canprovide position and speed feedback in order to enable rotationalstability and relatively fast placement of positioning structure 42 intoa stable position. Motor 60 may include a 4000 count/revolution encoderand worm drive 106 may have a gear ratio of 20:1, thereby achieving80,000 counts/revolution (i.e., 0.0045 degrees/count). Although a wormdrive configuration is described herein, it should be understood thatother gear mechanisms may be implemented in alternative embodiments.

As further illustrated in FIG. 6, shaft 92 is generally hollow in orderto form a passage, i.e., feedthrough port 90, through which a flexibleshaft 116 as well as signal wires 118 may be routed. Signal wires 118can form the physical connections between MEMS devices 22 (FIG. 1)installed in fixture 44 (FIG. 1) and test unit 30 (FIG. 1). As such,device output signals 52 (FIG. 1) can be communicated from MEMS devices22 to test unit 30 during testing, such as during tri-temp thermalconditioning.

Now referring to FIG. 7 in connection with FIG. 5, FIG. 7 FIG. 7 shows asimplified side view of another portion of rotational drive system 54implemented within the test system 20 (FIG. 1). In some embodiments,rotational drive system 54 includes motor 62, a transfer shaft, alsoreferred to herein as flexible shaft 116, and another worm drive 120that cooperatively function to rotate, or pivot, fixture 44 relative topositioning structure 42. Worm drive 120 includes a worm 122 coupledwith flexible shaft 116, which in turn is coupled with motor 62. Wormdrive 120 further includes a worm gear 124 coupled with shaft 100. Wormdrive 120 is a gear arrangement in which worm 122 (in the form of ascrew) meshes with worm gear 124. Accordingly, worm 122 includes threads126 that mesh with teeth 128 of worm gear 124.

In an embodiment, worm drive 120 is located within interior space 32(FIG. 1). As such, worm drive 120 is simplistically illustrated in FIG.5 coupled with shaft 100. As mentioned previously, motor 62 is locatedoutside of chamber 24 (FIG. 1) and flexible shaft 116 is directedthrough feedthrough port 90 (FIG. 6). Thus in FIG. 7, flexible shaft 116is shown in discontinuous form to represent its passage from motor 62,through feedthrough port 90, and coupling with worm 122.

In operation, flexible shaft 116 is driven to rotate by motor 62. Due totheir interconnection, worm 122 rotates along with flexible shaft 116.The relationship of threads 126 of worm 122 with teeth 128 of worm gear124 causes worm gear 124 to rotate when worm 122 rotates. Since wormgear 124 is coupled to shaft 100, shaft 100 also rotates along with wormgear 124. Furthermore, since shaft 100 is interconnected with fixture44, fixture 44 will also rotate, or pivot, to a desired position. Insome embodiments, motor 62 may also be a servomotor that includes amotor and a rotary encoder combination that forms a servomechanism.Motor 62 may be configured to achieved, for example, less than +/−0.1degree of rotational accuracy. Again, although a worm driveconfiguration is described herein, it should be understood that othergear mechanisms may be implemented in alternative embodiments.

FIG. 8 shows a cut away partial top view of positioning structure 42 oftest system 20 (FIG. 1). In some embodiments, some or all of beams 94,96, and 98 of positioning structure 42 includes a hollow region 130 inwhich flexible shaft 116 may be located. Flexible shaft 116 is capableof transmitting rotary motion between two objects, and in particular,between motor 62 (FIG. 7) and worm 122, which are not fixed relative toone another. Flexible shaft 116 may be formed from a rotating wire ropeor coil which is flexible, but has some torsional stiffness. As shown inthe cut away view of FIG. 8, beams 94 and 98 are shown as having hollowregion 130. Accordingly, flexible shaft 116 may be passed throughfeedthrough port 90, shaft 92, beam 98, and beam 94 to interconnect withworm 122.

Subsequent illustrations will present various positions in which fixture44 (FIG. 5) may be oriented during MEMS device testing in accordancewith testing methodology. The testing may entail tri-temp thermalconditioning or any other suitable test in which device output signals52 (FIG. 1) may be collected from MEMS devices 22 (FIG. 1) when MEMSdevices 22 are placed into the various positions.

FIG. 9 shows a simplified partial front view exemplifying positioningstructure 42 and fixture 44 of positioning apparatus 26 of test system20 (FIG. 1) placed in a first position 132. More particularly, FIG. 9 ispresented as looking inwardly toward thermal chamber 24 (FIG. 1) fromfeedthrough port 90. First position 132 may entail an orientation inwhich positioning structure 42 and fixture 44 are oriented such that aplanar surface 134 of fixture 44 is perpendicular to, for example, aZ-axis 136, within a three-dimensional coordinate system. As such,planar surface 134 of fixture 44 extends in two directions, i.e.,parallel to X-axis 56 and parallel to Y-axis 58. Z-axis 136 is directedup-and-down in FIG. 9. Whereas, Y-axis 58 extends right-to-left in FIG.9 and X-axis 56 extends inwardly into the page.

Precise position control of positioning structure 42 and fixture 44 maybe accomplished via motors 60 and 62 (FIG. 1), and feedback of firstposition 132 may be detected via position sensor 46 (FIG. 1). Forillustrative purposes, a single MEMS device 22 is shown in dashed lineformat installed on planar surface 134 of fixture 44. However, it shouldbe understood that a plurality of MEMS devices 22 may be loaded intofixture 44 as discussed in connection with FIG. 1.

FIG. 10 shows a simplified partial front view exemplifying positioningstructure 42 and fixture 44 of positioning apparatus 26 of test system20 (FIG. 1) placed in a second position 138. Like FIG. 9, FIG. 10 ispresented as looking inwardly toward thermal chamber 24 (FIG. 1) fromfeedthrough port 90. Second position 138 may entail an orientation inwhich positioning structure 42 and fixture 44 are oriented such thatplanar surface 134 of fixture 44 is perpendicular to, for example, aY-axis 58, within a three-dimensional coordinate system. As such, planarsurface 134 of fixture 44 extends in two directions, i.e., parallel toX-axis 56 and parallel to Z-axis 136. Z-axis 136 is directed up-and-downin FIG. 10. Y-axis 58 extends right-to-left in FIG. 10, and X-axis 56extends inwardly into the page.

Precise position control of positioning structure 42 and fixture 44 maybe accomplished via motors 60 and 62 (FIG. 1), and feedback of secondposition 138 may be detected via position sensor 46 (FIG. 1). Moreparticularly, motor 60 (FIG. 1) may be actuated to rotate shaft 92 (FIG.5) and thereby rotate, or pivot, positioning structure 42 and fixture44. Again, a single MEMS device 22 is shown in dashed line formatinstalled on planar surface 134 of fixture 44 for illustrative purposes.However, in actual practice, a plurality of MEMS devices 22 may beloaded into fixture 44.

FIG. 11 shows a simplified partial side view exemplifying fixture 44 ofpositioning apparatus 26 of test system 20 (FIG. 1) placed in a thirdposition 140. Third position 140 may entail an orientation in whichpositioning structure 42 and fixture 44 are oriented such that planarsurface 134 of fixture 44 is perpendicular to, for example, a X-axis 56,within a three-dimensional coordinate system. As such, planar surface134 of fixture 44 extends in two directions, i.e., parallel to Y-axis 58and parallel to Z-axis 136. Z-axis 136 is directed up-and-down in FIG.11. X-axis 56 extends right-to-left in FIG. 11, and Y-axis 58 extendsinwardly into the page.

Precise position control of positioning structure 42 and fixture 44 maybe accomplished via motors 60 and 62 (FIG. 1), and feedback of thirdposition 140 may be detected via position sensor 46 (FIG. 1). Moreparticularly, motor 62 (FIG. 1) may be actuated to rotate shaft 100(FIG. 5) and thereby rotate, or pivot, fixture 44 relative topositioning structure 42. A single MEMS device 22 is shown in solid lineformat installed on planar surface 134 of fixture 44 for illustrativepurposes. However, a plurality of MEMS devices 22 may be loaded intofixture 44 in actual practice.

Fixture 44 may be oriented into first, second, and third positions 132,138, 140 shown in FIGS. 9-11 during thermal testing in accordance withmethodology presented in connection with FIG. 12. Positions 132, 138,140 are orthogonal to one another for simplicity of analysis. In otherembodiments, thermal testing may be performed with fixture 44 orientedinto different positions that may be orthogonal relative to one anotherand/or may be compound angles. Positioning apparatus 26 enables testingof MEMS devices 22 in a plurality of positions in accordance with avariety of test methodologies. Furthermore, positioning apparatus 26enables testing of MEMS devices 22 in a plurality of positions withminimal operator handling.

FIG. 12 shows a flowchart of a temperature test process 142 performedusing test system 20 in accordance with another embodiment. Temperaturetest process 142 may be executed in order to test MEMS devices 22 in arange of positions and over a range of temperatures. By way of example,temperature test process 142 may be executed to perform tri-temp thermalconditioning in order to characterize, or test, the functionality ofMEMS devices 22 over a range of temperatures, typically between −55° C.and +180° C. Temperature test process 142 may be embodied as executablecode executed at control unit 28 (FIG. 1) by a test operator.

Temperature test process 142 begins with a task 144. At task 144, MEMSdevices 22 (FIG. 1) are loaded into fixture 44. Loading task 144 may beperformed utilizing pick and place techniques, or any suitable manual orautomated process and equipment.

Following task 144, a task 146 is performed. At task 146, positioningapparatus 26, and more particularly, positioning structure 42 with theattached fixture 44 are installed in thermal chamber 24. For example,receivers 88 (FIG. 5) of positioning apparatus 26 may be slid alongslide rails 78 (FIG. 2) until face section (FIG. 3) engages with thermalchamber 24 (FIG. 3). This movement may be performed manually by anoperator. However, some embodiments may entail a motor driven closuresystem (not shown).

Next, at a task 148, control unit 28 (FIG. 1) may be used by an operatorto place fixture 44 into a desired position, for example, first position132 (FIG. 9). By way of example, control software may be executed atcontrol unit 28 that provides X-axis and Y-axis control signals 68, 70(FIG. 1) to motors 60 and 62 to actuate respective worm drives 106, 120(FIGS. 6 and 7) in order to electronically control the position ofpositioning structure 42 and fixture 44. The actual position of fixture44 may be sensed by position sensor 46 and provided as feedback tocontrol unit 28 and/or rotational drive system 54.

Following task 148, a task 150 may be performed. At task 150, thetemperature of thermal chamber 24 is set in accordance with a particulartest protocol and fan 38 (FIG. 1) is activated. Again, by way ofexample, the control software executed at control unit 28 may providetemperature setting signal 66 (FIG. 1) to temperature control circuit 36(FIG. 1) to set the temperature of thermal chamber 24. The controlsoftware may also provide fan on/off signal 65 (FIG. 1) to fan controlcircuit 40 (FIG. 1) so as to activate, i.e., turn on, fan 38.

Temperature test process 142 continues with a query task 152. At querytask 152, a determination is made as to whether thermal chamber 24 hadreached the desired temperature setting. By way of example, temperaturesignal 72 (FIG. 1) may be provided from thermal chamber 24 totemperature control circuit 36. This temperature signal 72 may also beprovided to control unit 28. When a determination is made at query task152, that the temperature of interior space 32 (FIG. 1) of thermalchamber 24 has not yet reached the desired temperature setting, process142 continues with a task 154.

At task 154, process 142 is placed in a wait state for a predeterminedperiod of time. Eventually, program control loops back to query task 152to again check temperature signal 72. When query task 152 eventuallydetermines that the temperature of interior space 32 has stabilized atthe desired temperature setting in accordance with temperature settingsignal 66, temperature test process 142 continues with a task 156.

At task 156, fan 38 is deactivated. An operational fan 38 might imposemechanical, vibratory-type, noise on device output signals 52.Accordingly, the control software executed by control unit 28 mayprovide fan on/off signal 65 (FIG. 1) to fan control circuit 40 (FIG. 1)so as to deactivate, i.e., turn off, fan 38. Deactivation of fan 38 thusremoves this source of noise from device output signals 52.

Following task 156, process 142 continues with a task 158. At task 158,device output signals 52 (FIG. 1) are obtained at test unit 30 (FIG. 1)from MEMS devices 22. Device output signals 52 may be stored at testunit 30 for later analysis.

Next, a query task 160 is performed. At query task 160, a determinationis made as to whether testing at the current temperature is to beperformed with MEMS devices 22 in another position. When testing is tooccur in another position, process 160 continues with a task 162.

At task 162, rotational drive system 54 (FIG. 1) is electronicallycontrolled to orient fixture 44 into the next test position. By way ofexample, the control software executing at control unit 28 can provideX-axis and Y-axis control signals 68, 70 (FIG. 1) to motors 60 and 62 toactuate respective worm drives 106, 120 (FIGS. 6 and 7) in order toelectronically control the position of positioning structure 42 andfixture 44. The actual position of fixture 44 may be sensed by positionsensor 46 and provided as feedback to control unit 28 and/or rotationaldrive system 54. For illustrative purposes, during a first iteration oftask 162, fixture 44 may be oriented into second position 138 (FIG. 10).

Following task 162, program control loops back to task 158 to againobtain device output signals 52 at task 158, and to make anotherdetermination at query task 160 as to whether testing is to occur inanother position. Thus, execution of tasks 158, 160, and 162 oftemperature test process 142 enable testing of MEMS devices 22 inmultiple positions, e.g., first, second, and third positions 132 (FIG.9), 138 (FIG. 10), 140 (FIG. 11) at a single temperature setting forthermal chamber 24. When a determination is made at query task 160, thatthere is not another position in which MEMS devices 22 are to be tested,temperature test process 142 continues with a query task 164.

At query task 164, a determination is made as to whether there isanother temperature setting for which testing is to occur. When there isanother temperature setting, program control loops back to task 148 toagain place fixture 44 in an initial position, to set the temperature ofthermal chamber 24 at task 150, and to eventually obtain device outputsignals 52 at task 158 with fixture 44 placed in one or more positions.Thus, execution of query task 164 and loop back to task 148 enablestesting of MEMS devices 22 over a range of temperatures, for example inthe complete tri-temp range for ambient, hot and cold (−55 C to +180 degC). However, when query task 164 determines that there are no furthertemperature settings for which testing is to occur, temperature testprocess 142 continues with a task 166.

At task 166, the test results obtained through the execution oftemperature test process 142 may be analyzed to determine thefunctionality of the tested MEMS devices 22. Functionality may entail anautomated comparison of device output signals 52 to ensure signalaccuracy over a predetermined operational temperature range, to verifytrim/calibration parameters for MEMS devices 22, and so forth. Followingtask 166, temperature test process ends.

It is to be understood that certain ones of the process blocks depictedin FIG. 12 may be performed in parallel with each other or withperforming other processes. In addition, it is to be understood that theparticular ordering of the process blocks depicted in FIG. 12 may bemodified, while achieving substantially the same result. Accordingly,such modifications are intended to be included within the scope of theinventive subject matter. In addition, although particular systemconfigurations are described in conjunction with FIGS. 1-8, above,embodiments may be implemented in systems having other architectures, aswell. These and other variations are intended to be included within thescope of the inventive subject matter.

An embodiment of an apparatus includes a support structure, apositioning structure having first and second beams spaced apart fromone another, and a third beam interconnected with each of the first andsecond beams, and a fixture for retaining at least one MEMS device. Afirst shaft spans between the support structure and the positioningstructure. The first shaft is configured to rotate about a first axisrelative to the support structure in order to rotate the positioningstructure and the fixture about the first axis. A second shaft spansbetween the first and second beams of the positioning structure, and thefixture is retained on the second shaft. The second shaft is configuredto rotate about a second axis relative to the positioning structure inorder to rotate the fixture about the second axis, and the second axisis orthogonal to the first axis.

An embodiment of a test system for testing a MEMS device includes achamber and a support structure, the support structure including a facesection, the face section forming a sealable door for the chamber. Thetest system further includes a positioning structure and a fixture,where the positioning structure has first and second beams spaced apartfrom one another, and a third beam interconnected with each of the firstand second beams, and the fixture is configured to retain the MEMSdevice. A first shaft spans between the support structure and thepositioning structure. The first shaft is configured to rotate about afirst axis relative to the support structure in order to rotate thepositioning structure and the fixture about the first axis. A secondshaft spans between the first and second beams of the positioningstructure, and the fixture is retained on the second shaft. The secondshaft is configured to rotate about a second axis relative to thepositioning structure in order to rotate the fixture about the secondaxis, the second axis being orthogonal to the first axis. A rotationaldrive system enables rotation of the positioning structure about thefirst axis and enables rotation of the fixture about the second axis viaelectric power, wherein when the sealable door is attached to thechamber, the positioning structure resides inside the chamber, and atleast a portion of the rotational drive system resides outside of thechamber.

An embodiment of a method of testing a MEMS device includes loading theMEMS device into a fixture of a positioning apparatus, the positioningapparatus further including a support structure, a positioning structurehaving first and second beams spaced apart from one another, and a thirdbeam interconnected with each of the first and second beams, a firstshaft interconnected with each of the support structure and thepositioning structure, and a second shaft interconnected with the firstand second beams of the positioning structure, the fixture beingretained on the second shaft. The method further includes installing thepositioning apparatus into a test chamber, placing the fixture into afirst position, and obtaining a first output signal from the MEMS devicein the first position. The fixture is oriented into a second position,wherein the first shaft is configured to rotate about a first axisrelative to the support structure in order to rotate the positioningstructure and the fixture about the first axis, the second shaft isconfigured to rotate about a second axis relative to the positioningstructure in order to rotate the fixture about the second axis, thesecond axis being orthogonal to the first axis, and the orientingoperation includes rotating at least one of the positioning structureand the fixture about at least one of the first and second axes. Asecond output signal is obtained from the MEMS device in the secondposition and a functionality of the MEMS device is determined utilizingthe first and second output signals.

In summary, the various embodiments enable MEMS devices to be tested invarious positions and over a range of temperatures. The test systemincludes multiple axis control that minimizes operator involvement in atest process, such as thermal conditioning and/or calibration, whileachieving improvements in position accuracy, MEMS device throughput, andreduced test time. Accordingly, MEMS devices can be trimmed andqualification readouts can be performed at significant cost savings.

While the principles of the inventive subject matter have been describedabove in connection with specific apparatus and methods, it is to beclearly understood that this description is made only by way of exampleand not as a limitation on the scope of the inventive subject matter.The various functions or processing blocks discussed herein andillustrated in the Figures may be implemented in hardware, firmware,software or any combination thereof. Further, the phraseology orterminology employed herein is for the purpose of description and not oflimitation.

The foregoing description of specific embodiments reveals the generalnature of the inventive subject matter sufficiently so that others can,by applying current knowledge, readily modify and/or adapt it forvarious applications without departing from the general concept.Therefore, such adaptations and modifications are within the meaning andrange of equivalents of the disclosed embodiments. The inventive subjectmatter embraces all such alternatives, modifications, equivalents, andvariations as fall within the spirit and broad scope of the appendedclaims.

What is claimed is:
 1. An apparatus comprising: a support structure; apositioning structure having first and second beams spaced apart fromone another, and a third beam interconnected with each of said first andsecond beams; a fixture for retaining at least onemicroelectromechanical systems (MEMS) device; a first shaft spanningbetween said support structure and said positioning structure, saidfirst shaft being configured to rotate about a first axis relative tosaid support structure in order to rotate said positioning structure andsaid fixture about said first axis; and a second shaft spanning betweensaid first and second beams of said positioning structure, said fixturebeing retained on said second shaft, wherein said second shaft isconfigured to rotate about a second axis relative to said positioningstructure in order to rotate said fixture about said second axis, saidsecond axis being orthogonal to said first axis.
 2. An apparatus asclaimed in claim 1 wherein each of said first and second beams has afirst end and a second end, said third beam is interconnected with saideach of said first and second beams proximate to said first end, andsaid second shaft is interconnected with said each of said first andsecond beams proximate to said second end.
 3. An apparatus as claimed inclaim 1 wherein: said support structure and said positioning structureare configured to place said fixture in a first position in which aplanar surface of said fixture is perpendicular to a third axis, saidthird axis being perpendicular to each of said first and second axes;said first shaft is configured to rotate said support structure aboutsaid first axis to place said fixture in a second position in which saidplanar surface of said fixture is perpendicular to said second axis; andsaid second shaft is configured to rotate said fixture about said secondaxis to place said fixture in a third position in which said planarsurface of said fixture is perpendicular to said first axis.
 4. Anapparatus as claimed in claim 1 further comprising a position sensorcoupled to said fixture.
 5. An apparatus as claimed in claim 4 whereinsaid position sensor is configured to detect a first position of saidfixture relative to said first axis and a second position of saidfixture relative to said second axis.
 6. An apparatus as claimed inclaim 1 further comprising a rotational drive system for enablingrotation of said positioning structure about said first axis and forenabling rotation of said fixture about said second axis via electricpower.
 7. An apparatus as claimed in claim 6 wherein said rotationaldrive system comprises: a motor; and a worm drive including a worm and aworm gear, said worm being coupled with said motor, said worm gear beingcoupled with said first shaft, and said worm having threads that meshwith teeth of said worm gear.
 8. An apparatus as claimed in claim 6wherein said rotational drive system comprises: a motor; a transfershaft coupled with said motor; and a worm drive including a worm and aworm gear, said worm being coupled with said transfer shaft, said wormgear being coupled with said second shaft, and said worm having threadsthat mesh with teeth of said worm gear.
 9. An apparatus as claimed inclaim 8 wherein said transfer shaft comprises a flexible shaft.
 10. Anapparatus as claimed in claim 8 wherein each of said first and thirdbeams of said positioning structure includes a hollow region, and saidtransfer shaft is routed through said hollow region of each of saidfirst and third beams.
 11. An apparatus as claimed in claim 6 furthercomprising a controller for electrically controlling said rotationaldrive system to position said fixture relative to said first and secondaxes.
 12. An apparatus as claimed in claim 1 wherein said apparatus isconfigured to be placed in a chamber, and said support structurecomprises a face section, said face section forming a sealable door forsaid chamber such that when said sealable door is attached to saidchamber, said positioning structure resides inside said chamber.
 13. Anapparatus as claimed in claim 12 wherein: said face section comprises afeedthrough port; and said apparatus further comprises a rotationaldrive system for enabling rotation of said support structure about saidfirst axis and for enabling rotation of said fixture about said secondaxis, wherein said rotational drive system comprises a motor and atransfer shaft coupled with said motor, said transfer shaft being routedthrough said feedthrough port, and said transfer shaft being inmechanical communication with said second shaft.
 14. An apparatus asclaimed in claim 1 wherein said first, second, and third beams of saidpositioning structure are formed from a ceramic material.
 15. A testsystem for testing a microelectromechanical systems (MEMS) devicecomprising: a chamber; a support structure, said support structureincluding a face section, said face section forming a sealable door forsaid chamber; a positioning structure having first and second beamsspaced apart from one another, and a third beam interconnected with eachof said first and second beams; a fixture for retaining said MEMSdevice; a first shaft spanning between said support structure and saidpositioning structure, said first shaft being configured to rotate abouta first axis relative to said support structure in order to rotate saidpositioning structure and said fixture about said first axis; a secondshaft spanning between said first and second beams of said positioningstructure, said fixture being retained on said second shaft, whereinsaid second shaft is configured to rotate about a second axis relativeto said positioning structure in order to rotate said fixture about saidsecond axis, said second axis being orthogonal to said first axis; and arotational drive system for enabling rotation of said positioningstructure about said first axis and for enabling rotation of saidfixture about said second axis via electric power, wherein when saidsealable door is attached to said chamber, said positioning structureresides inside said chamber, and at least a portion of said rotationaldrive system resides outside of said chamber.
 16. A system as claimed inclaim 15 wherein said rotational drive system comprises: a dual axismotor; a first worm drive including a first worm and a first worm gear,said first worm being coupled with said dual axis motor, said first wormgear being coupled with said first shaft, and said first worm havingfirst threads that mesh with first teeth of said first worm gear; atransfer shaft coupled with said dual axis motor; and a second wormdrive including a second worm and a second worm gear, said second wormbeing coupled with said transfer shaft, said second worm gear beingcoupled with said second shaft, and said second worm having secondthreads that mesh with second teeth of said second worm gear.
 17. Asystem as claimed in claim 16 wherein: said second worm drive ispositioned within said chamber; said face section comprises afeedthrough port; said transfer shaft comprises a flexible shaft; andeach of said first and third beams of said positioning structureincludes a hollow region, and said flexible shaft is routed through saidfeedthrough port and through said hollow region of each of said firstand third beams to couple to said second worm of said second worm drive.